If it was one folder, I'd go with the Spyderco Farid Mehr K2 -- firstly, based on the 'you can do small jobs with a big knife, but you can't do big jobs with a small knife' principle; secondly, because it's a blade design that's optimal for deep slicing, quick slashing, AND stabbing; thirdly, the CPM 10V blade steel has crazy edge-retention properties and impressive toughness; lastly, it has a Sebenza-like simplicity of design that allows easy cleaning and maintenance, and has very little that CAN go wrong with it.
If it's a fixed-blade, the Bark River Bravo III, for almost exactly the same reasons I'd take the K2: it's huge enough to be a machete, a battle-sword, a log-splitter, but with excellent ergonomics that make it great for smaller jobs as well; the CPM 3V is perfect for the scaled-up dimensions; and while it's not exactly made for stabbing, it can still pierce effectively... but when it comes to hacking at enemies, it's a monster, a chopping tool that's built for battlefield brutality.
Edit: I'm not military, and never will be. So for me, the battlefield would be my own backyard, a combination of heavily forested wilderness and small cities. This is all speculation about stuff that's about as likely as the Rapture, so I'm not real concerned about differences of opinion. I find it pretty funny, however, that some people like to get all smug and self-righteous about big knives, or claim that it doesn't matter what knife you bring to the battlefield. WTF are you doing in this thread? This forum? People who spend a lot of time thinking about EDC options in peace-time suddenly lose all need for a knife in a warzone? Whatever. I carry around a ZT 0561, a Spyderco Manix 2 XL, or a Spyderco K2 for an EDC, and a couple extra ounces do not bother me in the least. If I do that living in one of the safest and stable countries on the planet, I'll sure as hell make room for a chopper in a warzone, if things suddenly went straight to hell. That said, big knives aren't as useful in the desert environment of the Middle East as they are in forests or jungles, obviously. I'm not thinking about the Middle East, and I don't plan on picking a fight with any desert-dwellers... even though ISIS are the most infuriating assholes on the planet.
